The present invention relates to locksets in general, and, more in particular, to double bolt locksets that simultaneously lock and unlock and have a panic unlock feature.
Locksets for locking doors against entry have taken a variety of forms. One form uses a key and a knob. This lockset has a spring-latch bolt biased to an extended position so that upon closing a door the latch extends into a mortise and keeps the door shut. The latch bolt can be locked to lock the door. The projection of the latch bolt, however, is short, leading to ease in springing the door or door jam and unwanted entry. In addition, this type of lockset generally is easily broken; for example, the knob can be pried off to expose the latch to easy retraction.
A second type of lockset is a mortise lock. These locks are considerably less vulnerable and are of much stronger construction than key-in-the-knob locks. These locks, too, have fallen into disfavor in recent years. One disadvantage is that a mortise lock requires a large cut-out space in the door to receive a large lock case that contains the lock mechanisms. The space in the door weakens the door. A good hard kick near the lock can often split the door and permit entry. Mortise locks are also expensive to install and to make.
A dead bolt lock is a third type of lockset. The dead bolt may be extended and retracted with a key from outside of a door and on the inside by an operator such as a thumb piece or thumb turn. A well-constructed dead bolt lock offers the best security of any of the locks discussed here. A dead bolt lock does not have the large cut-out space required by a mortise lock, and can project a substantial amount into a deep hole of an associated mortise in the door jam. One problem with dead bolts is that they require a spring latch bolt to retain the door closed when the dead bolt is retracted and the door unlocked. Operating both the dead bolt and the spring latch can be awkward.
Notwithstanding this defect in dead bolts, it has been the trend in recent years to construct locksets by combining both a dead bolt and a spring latch bolt. Some of these constructions have only the dead bolt locking. Others lock both the dead bolt and the latch bolt.
There is substantial inconvenience in a double locking lockset in having to independently unlock both the latch bolt and a dead bolt. Some constructions employing both a dead bolt and a latch bolt simultaneously retract both the dead bolt and the latch bolt by actuation of a single inside operator, such as an inside knob.
U.S. Pat. No. 3,910,613 to Roger Nolin describes a very simple lock that permits the simultaneous opening of a spring latch and a dead bolt in a surface-mounted lockset. But the patent does not describe a simultaneously locking and unlocking latch bolt and dead bolt.
Simultaneous locking and unlocking locksets are shown in mortise-type locks, such as in U.S. Pat. No. 3,337,248 to Fred J. Russell and Roger J. Nolin. In mortise-type locks, all the components, the dead bolt mechanisms, latch bolt mechanisms, key mechanisms, and retracting mechanisms, are located in the same case in close proximity to each other. Accordingly, it is comparatively easy to arrange the components at will to achieve the dependence necessary for simultaneous operation. Even with the attraction of mortise-type locks and the ability to simultaneously lock and unlock both the dead bolt and a latch bolt, these locks still offer poor security, and have the disadvantage of high installation and construction costs.
It is also a highly desirable feature in a lockset to provide for a panic-proof exit--to leave in a hurry in case of fire, for example. This type of lockset retracts both the lock bolt and latch bolt with a single operation of a hand operator on the inside of the door. U.S. Pat. No. 3,910,613, referenced above, is an example of such a panic-proof lockset.
U.S. Pat. No. 3,791,180 to William J. Doyle illustrates a different construction of a panic-proof feature in a surface-mounted lockset. This construction uses a gear sector to interconnect dead bolt and latch bolt assemblies. The construction has separately keyed lock bolts and latch bolts. Doyle does not provide for simultaneous locking and unlocking of both a dead bolt and a latch bolt with but a single operation from either inside or outside of a door.
U.S. Pat. No. 4,183,563 to Stevens discloses a panic-proof lockset that employs a double-lobed cam operatively connected to an inside hand operator and which couples to a slide to effect withdrawal of a dead bolt upon actuation of an inside hand operator. The slide is loaded in tension against the double lobes of the cam to maintain position. A shoulder of the slide bears on a crank of the dead bolt assembly. Rotation of the double-lobed cam in either direction displaces the slide downwardly and rotates the crank to withdraw the dead bolt. A slot in the slide receives the crank in the dead bolt's withdrawn position. The Stevens patent does not disclose means for simultaneously locking and unlocking a lockset in addition to a panic-proof feature.
U.S. Pat. No. 3,390,558 to Tornoe et al shows a complicated lock having many desirable features. It is panic-proof and has a latch bolt and dead bolt that can be simultaneously opened from either the inside or the outside of a door. This construction, however, does not provide a lockset that has a latch bolt and a dead bolt that simultaneously lock or unlock. The latch bolt is independently locked with a push turn button on the face of the inside knob. Turning the outside key retracts the dead bolt and the latch bolt, but the latch bolt remains locked. The control of the knob face has to be manually operated to unlock the latch bolt.
The parent of this application describes a lockset of a dead bolt and a spring latch bolt that simultaneously lock and unlock, and has a panic-proof feature. A crank mounts on a dead bolt assembly. During locking, the crank rotates and engages a slide that moves to engage a latch actuator with a tooth to lock the latch bolt. Springs bias the slide in a direction out of engagement with the actuator so that rotation of the crank away from the slide frees the slide, and it moves out of engagement with the actuator to unlock the latch bolt. Because the latch actuator must rotate to unlock the latch bolt and because it must be unlocked before rotation of the inside hand operator can open the latch bolt, lost motion is necessary between the inside hand operator and the actuator. To this end and to open the dead bolt, a retractor carries the slide and the springs that bias the slide away from engagement with the actuator. The retractor is spring biased towards the latch bolt assembly. The inside hand operator operates a cam that engages the retractor to produce translation of the retractor against the bias. With this movement of the retractor, the slide moves away from the actuator, and rotates the crank of the dead bolt assembly from its locked to its unlocked position. Retractor movement during this unlocking effects withdrawal of the tooth of the slide from the actuator prior to rotation of the actuator by a dog of the cam acting on a follower of the actuator: the lost motion. With rotation of the actuator, the latch bolt retracts.